    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *     http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.configuration2.io;
    018
    019import java.io.File;
    020import java.net.URL;
    021
    022import org.apache.commons.lang3.StringUtils;
    023
    024/**
    025 * <p>
    026 * A specialized implementation of {@code FileLocationStrategy} which searches
    027 * for files in the user's home directory or another special configurable
    028 * directory.
    029 * </p>
    030 * <p>
    031 * This strategy implementation ignores the URL stored in the passed in
    032 * {@link FileLocator}. It constructs a file path from the configured home
    033 * directory (which is the user's home directory per default, but can be changed
    034 * to another path), optionally the base path, and the file name. If the
    035 * resulting path points to an existing file, its URL is returned.
    036 * </p>
    037 * <p>
    038 * When constructing an instance it can be configured whether the base path
    039 * should be taken into account. If this option is set, the base path is
    040 * appended to the home directory if it is not <b>null</b>. This is useful for
    041 * instance to select a specific sub directory of the user's home directory. If
    042 * this option is set to <b>false</b>, the base path is always ignored, and only
    043 * the file name is evaluated.
    044 * </p>
    045 *
    046 * @version $Id: HomeDirectoryLocationStrategy.java 1842194 2018-09-27 22:24:23Z ggregory $
    047 */
    048public class HomeDirectoryLocationStrategy implements FileLocationStrategy
    049{
    050    /** Constant for the system property with the user's home directory. */
    051    private static final String PROP_HOME = "user.home";
    052
    053    /** The home directory to be searched for the requested file. */
    054    private final String homeDirectory;
    055
    056    /** The flag whether the base path is to be taken into account. */
    057    private final boolean evaluateBasePath;
    058
    059    /**
    060     * Creates a new instance of {@code HomeDirectoryLocationStrategy} and
    061     * initializes it with the specified settings.
    062     *
    063     * @param homeDir the path to the home directory (can be <b>null</b>)
    064     * @param withBasePath a flag whether the base path should be evaluated
    065     */
    066    public HomeDirectoryLocationStrategy(final String homeDir, final boolean withBasePath)
    067    {
    068        homeDirectory = fetchHomeDirectory(homeDir);
    069        evaluateBasePath = withBasePath;
    070    }
    071
    072    /**
    073     * Creates a new instance of {@code HomeDirectoryLocationStrategy} and
    074     * initializes the base path flag. The home directory is set to the user's
    075     * home directory.
    076     *
    077     * @param withBasePath a flag whether the base path should be evaluated
    078     */
    079    public HomeDirectoryLocationStrategy(final boolean withBasePath)
    080    {
    081        this(null, withBasePath);
    082    }
    083
    084    /**
    085     * Creates a new instance of {@code HomeDirectoryLocationStrategy} with
    086     * default settings. The home directory is set to the user's home directory.
    087     * The base path flag is set to <b>false</b> (which means that the base path
    088     * is ignored).
    089     */
    090    public HomeDirectoryLocationStrategy()
    091    {
    092        this(false);
    093    }
    094
    095    /**
    096     * Returns the home directory. In this directory the strategy searches for
    097     * files.
    098     *
    099     * @return the home directory used by this object
    100     */
    101    public String getHomeDirectory()
    102    {
    103        return homeDirectory;
    104    }
    105
    106    /**
    107     * Returns a flag whether the base path is to be taken into account when
    108     * searching for a file.
    109     *
    110     * @return the flag whether the base path is evaluated
    111     */
    112    public boolean isEvaluateBasePath()
    113    {
    114        return evaluateBasePath;
    115    }
    116
    117    /**
    118     * {@inheritDoc} This implementation searches in the home directory for a
    119     * file described by the passed in {@code FileLocator}. If the locator
    120     * defines a base path and the {@code evaluateBasePath} property is
    121     * <b>true</b>, a sub directory of the home directory is searched.
    122     */
    123    @Override
    124    public URL locate(final FileSystem fileSystem, final FileLocator locator)
    125    {
    126        if (StringUtils.isNotEmpty(locator.getFileName()))
    127        {
    128            final String basePath = fetchBasePath(locator);
    129            final File file =
    130                    FileLocatorUtils.constructFile(basePath,
    131                            locator.getFileName());
    132            if (file.isFile())
    133            {
    134                return FileLocatorUtils.convertFileToURL(file);
    135            }
    136        }
    137
    138        return null;
    139    }
    140
    141    /**
    142     * Determines the base path to be used for the current locate() operation.
    143     *
    144     * @param locator the {@code FileLocator}
    145     * @return the base path to be used
    146     */
    147    private String fetchBasePath(final FileLocator locator)
    148    {
    149        if (isEvaluateBasePath()
    150                && StringUtils.isNotEmpty(locator.getBasePath()))
    151        {
    152            return FileLocatorUtils.appendPath(getHomeDirectory(),
    153                    locator.getBasePath());
    154        }
    155        return getHomeDirectory();
    156    }
    157
    158    /**
    159     * Obtains the home directory to be used by a new instance. If a directory
    160     * name is provided, it is used. Otherwise, the user's home directory is
    161     * looked up.
    162     *
    163     * @param homeDir the passed in home directory
    164     * @return the directory to be used
    165     */
    166    private static String fetchHomeDirectory(final String homeDir)
    167    {
    168        return (homeDir != null) ? homeDir : System.getProperty(PROP_HOME);
    169    }
    170}